Producing scales, patterns and the like in glass



March 1, 1960 A. J. c. HALL ETAL 2,927,042

PRODUCING SCALES, PATTERNS AND THE LIKE IN GLASS Filed Feb. 16, 1956 2 sheets-sheet 1 ATTORNEYS March 1, 1960 A. J. c. HALL ETAL 2,927,042

PRODUCING SCALES, PATTERNS AND THE LIKE IN GLASS Filed Feb. 16, 1956 2 Sheets-Sheet 2 /5 Naw /A/ 771/5 Gla/L55 ...Ann-.....n-.An

ATTORNEYS PRODUCING SCALES, PATTERNS AND THE LIKE IN GLASS Arthur John Charles Hall, Bentleigh, Victoria, and James Godfrey Hayes, Hawthorn, Victoria, Australia, assignors to Commonwealth of Australia, Crown Solicitors Oflice, Canberra, New South Wales, Australia Application February 16, 1956, Serial No. l565,789

l Claims priority, application Australia February 25, 1955` 411 Claims. (Cl. 117-38) This invention relates to an improved method of producing scales, patterns and the like and lrefers more particularly `tothe production of scales, patterns, graticules and other markings in glass for optical instruments and for other purposes.

Graticules, scales and other patterns or markings on or in glass, are used for a variety of applications in the fields of science and industry and for the armed services, and several methods of making them have been established, as follows:

A. A layer of material resistant to an etching fluid such as hydrofiuorio acid is deposited on the glass, the desired patternis formed in the resistant material by mechanical ruling, etching liuid is applied to etch the glass exposed by such ruling and then the etched pattern is filled with a suitabletilling material. Alternatively the pattern may bel formed in a suitable resist `by the use of materials such as photo-engravers glue, before the glass is etchedand then filled.

B. The pattern may be deposited on the glass by physical and/or chemical methods as for example by evaporation of a metal onto the glass through a suitable mask or by using photo-sensitive glue and ferric nitrate solution to form the pattern in a metal that has already been deposited on the glass or by colouring the pattern formed in photo-sensitive glue on the glass. Y

C. The pattern may be formed by conventional photographic means in the emulsion of photographic plate or film and the plate or film then cut to the desired shape or the emulsion stripped ofi and redeposited on a glass disc.

D. Lines may beiruled directly into glass as,` with a diamond tool or through a layer of opaque material deposited on glass.

ln general the most satisfactory graticules have been those made by method (A) above, such graticules being less liable to damage and deterioration than the other types which are readily damaged by moisture, abrasion or fungi unless protected by a cover slip which is often undesirable. Graticules made by ruling directly into glass with a diamond tool have limited usefulness because only extremely thin lines can be made in this way and they are `not generally useful. Graticules of type (A) t are not ideal in that portions of the filling in the lines This is particularly so when the pattern is complicated and 'contains figures as most graticules do.

It is an object of this invention to provide a method of producing scales, patterns and the like in glass which is particularly useful for the manufacture of graticules `in'that it overcomes the above disadvantages, and which United safes Pat-em o ice is also useful for other purposes such as the marking and graduating of glass articles suchas thermometer stems, burettes and syringe barrels.

A method of producing scales, patterns" and the like according to theinvention broadly comprises forming the scale, pattern or the like in metal or metallic compound on the surface of the glass, and by suitable means causing the final scale, pattern or the like to be formed within the glass.

More particularly a method according to the invention may comprise forming the scale, pattern or the like in metal or metallic compound on the surface of the glass,

. exposing the glass to oxidizing conditions such as will form a latent image of the scale, pattern or the like within the glass, and thereafter exposing the latent image to conditions such as will develop the scale, pattern or the like in a visible state within the glass. Silver has been found to be the most suitable metal for carrying out the invention. Copper also is Very satisfactory and it appears that other metals such as gold, for example, may be usefulj As well as the metals themselves, metallic compounds, such as chlorides and sulphates, can :be used.

`Two methods of forming patterns on glass are illustrated in the accompanying drawings and will be more fully described hereinafter. Briefly Fig. 1 diagrammatically illustrates' a piece of glass with a metallic pattern on its surface,

iFig. 2 shows the glass and pattern of Fig. l in affurnace where it is `to be heated and subjected to an atmosphere containing sulfur trioxide,

Fig. 3 shows the glass after the-treatment illustrated in Fig. 2, i

Fig. 4 shows the glass with the visible pattern after a reduction treatment in the furnace,`

Fig. 5 is similar to Fig. l,

Fig. 6 shows the glass bearing the metallic pattern, prepared by coating with graphite for subsequent oxidation by electrolytic treatment,

Fig. 7 illustrates the electrolytic treatment,

Figs. 8 and 9 illustrate the effect of the electrolytic treatment, and

Fig. l0 illustrates the final reduction step.

The original step of depositing the desired final pattern iti-metal or metallic compound on the surface of the glass can be effected by any suitable means. For example the glass may be .coated with a film of a suitable metal or metallic compound and this film then coated with a film of photo-sensitive material such as photo-engravers glue. The treated surface is then exposed to suitable light `througl'l a negative of the desired pattern which has been prepared by suitable means. The photo-sensitive material which has not been exposed to the light is removed by known means and the metal or metallic compound film underlying it is also removed by known means, thereby leaving the desired pattern in the metal or metallic compound on the surface of the glass. Alternatively the desired final pattern in metal or metallic compound may be deposited on the glass by other suitable means such as for example by evaporation of metal or metallic compound onto the glass through the pattern which has been previously formed in photo-engravers glue, followed, if desired, by subsequent removal of photo-engravers glue and metal or metallic compound not wanted in the final pattern.

By one particular method according to this invention the formation of the latent image in the glass is achieved by subjecting the glass with the metal or metallic compound thereon to heat in an atmosphere that is acidic and capable of causing oxidation. Such atmospheres can be obtained from a number of substances but the best and most convenient to use has been found to be one containing sulphur trioxide, S03, which is conveniently Patented Mar. 1, 1&6()-

menaces Examples of other substances -that have been used successfully are, chlorine, bromine, phosphoryl chloride, and sulphuryl chloride. Suitable atmospheres have been obtained by heating ferrie sulphate, sulphuric acid, sodium bisulphate, and phosphorus pentoxide.

Good latent images have been-obtained by heating the glass with the metal or metallic compound thereon in an atmosphere containing a low concentration of sulphur trioxide in air at temperatures as low as 200 C. and as high `as 500 C. for periods ranging from 30 seconds to twenty minutes or even longer. To obtain the best v results the temperature at which, and the time for which,

the metal or metallic compound on the glass is exposed to the atmosphere containing the sulphur trioxide, have to be selected and they depend on the type of pattern and other factors such as type of glass, concentration of sulphur trioxide, type of metal or metallic compound, thickness of metal or metallic compound, andamount of lateral diffusion permissible.

After forming the latent image the gla'ss is then lexposed to a reducing atmosphere such as hydrogen or coal gas at about the same temperature. In this step the temperature range can be varied widely but the bestresults for our purposes -have 4been obtained at 400 C. This stepcauses the Vlatent scale orpattern to be developed withirrthe glass.

The duration of the latter step in the process depends markedly upon thetemperature and can be vas short as two minutes with temperatures-ofthe order of 500 C. but our bestresults have generally been obtained in from fifteen to twenty-ve minutes at 400 C. The glass may be allowed to cool between the two heating stages/and cleanedof any surplus material -on the surface but'this is not essential and the second heating step may directly follow the tiret. f'A-plant for the continuous treatment of glasses may be set up byarranging for the glasses to travel slowly through a twostage loven or furnacein which the required atmospheres are maintained in the two-stages.

By a second particular method according to this invention the formation of the 'latent image in the 'glass is achieved by subjecting the glass with the metal or metallic compound thereon to a suitable alternating current or direct current potential. For example we have found that by making suitablecontacts between the anode and cathode of a circuit with the faces of Va glass disc kept at 40G-500 CE-and having on one faceapattern in metal or rnetallic'cotnpound and thenapplyinga potential of 2000 vvolts D.C. for l5 seconds 'that with somernetals such as silver-and copper a latent image of the 'pattern is yformedwithin the glass; with other metals such as gold a visible image is formed in the glass. At the same temperature but with varying times of treatment similar resultshave been obtained with other potentials such as 110 volts and 45 volts and evenas low as 6 volts.

Just as in our rst method temperature, time and other conditions have to be selected to give a desired'result. So also in this second method the results obtained depend on temperature, time and potential used. For example at 300 C. a treatment for 30 minutes at 110 volts D.C. gave a good latent image vfor our purposes. When a latent image is formed it is capable of being converted into 'a visible image by reduction'in hydrogen at an elevated temperature.` as already described or by another method to bel described later.

In addition to the method already described for rcducing :latentlimages -to visiblelima'ges, this result can also be `z'tchie'ved*by?exposinga latent image to bombardment by electrons; the yelectrons may beobtained from any convenient source. 'lFor example, "we have.y found that a latent' imagej'formed from silver, when -heated at about 500 C. and simultaneouslyi bombarded withX-rays for l5 minutes'was converted into a visible image*.vithout the necessity to usehydro'gengas. :This'inethod of 011- verting the latent image to a visible image isapplicablev irrespective of the method used to form the latent image.

Unlike those produced by previously known methods the scales, patterns and the like produced by means of this invention are developed within the glass so that the pattern forming material isenclosed by,.and.is an integral part of the glass.

Structurally, glass consists of an irregular network of silica tetrahedra 'in which oxygen ions are present inftwo forms, namciy, those linking two vsilicon ions and those not linking two silicon ions but which are associated with weak spots or holes in the network. Network modifying ions such as .those of sodium, are situated inrsome of these interstices or holes and can migrate from one to another and can even leave the glass byway of the surface. These processes are assisted bya risefin temperature, by the presence `of suitable agents in contact with the glass orby the application of a suitable potential.

Under suitable conditions ions of appropriate size and charge, such as those of silver and copper, canibeymade to migrate from the surface of the glass into the interstices or holes and'so become part ofthe structure of `the glass. This occurs in the rst stage of our process in which also theremoval of modifying ions is assisted by the presence of anionic and oxidising conditionsat the surface Vof theiglass or by the application of asuitable potential across the glass. in the second stage-of Aour process the appropriate metallic ions, such as those of silver and copper which are now Within the glass, `are reduced to the atomic condition by the action of an electron donor such as hydrogen or directly by electron bombardment; the application of heat causes the atoms to aggregate and. so form a visible pattern.

yGraticuies and other scales and patterns made by these processes lare permanent in that they are resistant to abrasion, fungi, moisture, chemicals, steam or corrosive or deteriorating agents, nor do they need to be covered by a cover'slip. Because the .pattern is .an integral .part of the .glass the Vquestion of adhesion of the pattern to the glass .does not arise and the pattern is damaged only when the glass itself is damaged. It has been shown,for example, that such `a pattern. formed with silver, a metal which is normally attacked rapidly by concentrated nitric acid is unaffected by prolonged immersion in concentrated nitric acid. .These scales and patterns can bemade 1n a variety of colours, are pleasing in appearance and have none of .thedisadvantages of otliertypes ofV scalesv and patterns. They have been made successfully using several diiferent types of glass.V I

-A further advantage of the invention .is that VV1t is not necessary to take great care to prevent development of' defects inthose arcas surrounding the pattern, as 1s 'necessary in the case of most existing processes. The

invention will thus enable graticules and the like to be produced more economically than hither-to and on a mass production scale.

The examples given below serve to illustrate the manner in'which the invention may be applied. As we have previously Iindicated the desired initial pattern in metal or .metalliccompound may be formedonthe surface of the glass .by a number of methods, and Whenforminga graticule pattern in silver we have yfound that a single coat of silver deposited bythe Brashear process gives satisfactory results for most` purposes; under these conditions the-.thickness lof .the `silver :deposit would lbe approximately 0.1M. The thicknessof the deposit "of metal or metallic compound.;maybe varied Ato'.` suit, re; quirernenta To provide a` suitablenatmosphcre. forxthe `airstl stage vof the process, 'when using ourrstemethoi we have found it convenient .to use sulphundioxideiwhich is released from a cylinder .into a streamof-,airt approx-i matelyV 2% is sufcient).

`After mixing and drying, the'gases werepassed through platinized :quartz maintained.-l at a temperature;l hfY 400e- 450 C., before entering'. the. furnace'.vvhereiithe-:iiirst 'to-resist and ferrie nitrate. The glass with the silver on i it was then heated in a stream of air to 450 C. At this stage the supply of sulphur dioxide to the catalyst tube was turned on for 10 minutes, the temperature being maintained at 450 C.

The sulphur dioxide stream was -then turned off and after about one minute the glass was withdrawn from the furnace, cleaned by wiping and reduced in hydrogen for 25 minutes at 400 C. This procedure is suitable for fairlycoarse patterns and may be shortened by raising the reduction temperature if desired. By reducing the time for the first stage to 30 seconds, patterns of line lines could be made but better results were obtained by the procedure given in the next example.

Example II Glass coated with a silver pattern as in Example I was heated in the atmosphere containing sulphur trioxide for a period of 20 minutes at a temperature of 300 C. At the end of this time no metallic silver remained on the glass. in hydrogen at 400 C. for 25 minutes. Patterns of dense lines with sharp edges and 0.0005" wide resulted.

Example III As an illustration of the eiect of varying the temperature of reduction a number of patterns in silver were given the same initial treatment and then reduced at various temperatures from 150 C. to 470 C. It was found that attemperatures of 450 C., or above, reduction occurred within two minutes, yor even less, but for tine patterns better results were obtained by heating at 400 C. for longer periods between 15 and 25 minutes. At still lower temperatures the time required for reduction is longer and may not be accompanied by satisfactory aggregation of the reduced metallic atoms.

Example IV As an illustration of the use of a metallic compound to form the final pattern, a pattern was formed in glass by evaporation of silver chloride in vacuo. Application of the process for tive minutes at 450 C. in the rst stage and for twenty tive minutes in the second stage resulted in the formation of permanent patterns within the glass. One pattern formed consisted of tine clear lines in a green transparent background.

Example V As an illustration of the use of copper a pattern was formed in copper on Crystalex glass and application of the process as in Example IV resulted in the formation of a dark coppery red pattern within the glass.

Example VI As a further illustration of the variety of types of lines (that can be formed by this process some patterns of silver .on barium light flint glass were prepared and processed :as in Example 1V. The lines forming the nal pattern were very attractive in appearance; they consisted of a .central transparent portion which was very light yellow in colour, surrounded by a very dark, well dened edge.

Example VII Illustrating the application of the process -to various i types of glass, patterns of copper and silver were formed by evaporation onto borosilicate crown glass, barium flint glass, and dense lead int glass. In another ex- ;periment a pattern was produced by etching a silver The glass was wiped clean and was then heated film` `deposited on Pyrex` glass.y In all cases applicaf tion of the process resulted in the formation of perma nent patterns within the glass; the patterns were of various colours including dark brown, light yellow brown, grey-green and light coppery red.

. t .Example V111 Example IX A potential of 50 volts A.C. was applied for 5 minutes across a disc of plate glass having on each side of it a pattern in silver and kept at approximately 450 C. Silver remaining on the surface of the glass was then removed by immersion in nitric acid.

The glass disc containing the latent images was then reduced in hydrogen gas thereby forming visible images of the original patterns within the glass.

We claim:

1. A method of producing a visible image of a pat` tern, scale or the like within glass which comprises the steps of, forming said pattern or scale as a corresponding coating on the surface of the glass, said coating being a substance of the group consisting of gold, silver and copper and their salts, subjecting said coating to oxidizing conditions at a temperature within the range of 200 to 500 centigrade to cause ions of the metal of said coating to penetrate into the glass, and subjecting said glass to reducing conditions at a temperature within the range of 200 to 500 centigrade.

2. A method of producing a visible image within glass as defined in claim l wherein the step of subjecting said coating to oxidizing conditions is constituted by exposing said coating to an acidic atmosphere.

3. A method of producing a visible image within glass as dened by claim 2 wherein said acidic atmosphere contains sulphur trioxide.

4. A method of producing a visible image within glass as defined by claim 1 wherein the step of subjecting said coating to oxidizing conditions yis constituted by application of an electric potential to the coated surface of the glass at a temperature within the range of from 300 to 500 centigrade.

5. A method of producing a visible image within glass as defined by claim 1 wherein the step of subjecting said glass to reducing conditions is constituted by exposing the same to a reducing atmosphere containing hydrogen.

6. A method of producing a visible image within glass as dened by claim 5 wherein said reducing atmosphere is maintained at a temperature of about 400 centigrade for a period of from 15 to 25 minutes.

7. A method of producing a visible image within glass as defined by claim 1 wherein the step of subjecting said glass to reducing conditions is constituted by bombardment of the same with electrons.

8. A method of producing a visible image within glass as deiined by claim 7 wherein said electron bombardment is effected at -a 'temperature of about 500 centigrade for a period of about 15 minutes.

9. A method as defined in claim 1 in which the substance is silver.

10. A method as defined in claim 1 in which the substance is copper.

11. A method of producing a visible image of a pattern such as a scale or the like within glass which comczorresponding-V coating of metallicY goldon thet surfaces of the glass, and` exposing saidlcoatedsurfacefto oxidiz ingf conditionsy by. application. off an electrical Y potential thereto at a temperature withinltherange ofi400f to 50H03 centigrade to cause said gold to penetrate into the Yglass and establish a visible image therein corresponding to said coating.

References Cited inr the file of'this patent UNITED STATES PATENTS Schirmer vMar. 2419363 Leibg V V.... Mar. 30; 19'37 Damiltpn v r June 17, 1947 Meyer 1 1-- Iuly 15; 1947 McCallum l 2 NQv. 24; 195s` 

1. A METHOD OF PRODUCING A VISIBLE IMAGE OF A PATTERN, SCALE OR THE LIKE WITHIN GLASS WHICH COMPRISES THE STEPS OF, FORMING SAID PATTERN OR SCALE AS A CORRESPONDING COATING ON THE SURFACE OF THE GLASS, SAID COATING BEING A SUBSTANCE OF THE GROUP CONSISTING OF GOLD, SILVER AND COPPER AND THEIR SALTS, SUBJECTING SAID COATING TO OXIDIZING CONDITIONS AT A TEMPERATURE WITHIN THE RANGE OF 200* TO 500* CENTIGRADE TO CAUSE IONS OF THE METAL OF SAID COATING TO PENETRATE INTO THE GLASS, AND SUBJECTING SAID GLASS TO REDUCING CONDITIONS AT A TEMPERATURE WITHIN THE RANGE OF 200* TO 500* CENTIGRADE. 